Polikarpov I-15
The Polikarpov I-15 was a Soviet gull-wing biplane fighter of the 1930s, designed as the manoeuvrable dogfighter in a two-type fighter doctrine. First flown in October 1933, it fought for the Republicans in the Spanish Civil War, where Spanish pilots named it Chato, "snub-nose", and later in China and Mongolia, but it was outclassed by newer monoplanes before the Second World War began. Its developments, the I-15bis and I-153, kept the family in service into the 1940s, and a few I-153s survive, some of them flying.
Why It Mattered
The I-15 was the dogfighter in a two-part Soviet fighter doctrine of the 1930s: fast monoplanes would break up enemy formations, and manoeuvrable biplanes would then take advantage of the confusion to dogfight the scattered aircraft. It was a gull-winged biplane, a shape that earned it the Soviet nickname Chaika, "gull". The type made its name in Spain, where it fought for the Republican cause and Spanish pilots named it Chato, "snub-nose". Together with the I-16 monoplane it was one of the standard Republican fighters of the Spanish Civil War. By the spring of 1938 it was already becoming outclassed there, and most Soviet I-15s had left front-line service by June 1941.
Design Notes
Polikarpov's bureau began work in February 1933 on a biplane to replace his own I-5; the design was designated I-15, with the bureau designation TsKB-3. The result was a single-bay sesquiplane, its lower wing much smaller than the upper, with a fixed undercarriage and open cockpit. Its gulled upper wing had no centre section and was connected directly to the upper fuselage, which cut the drag of a centre section and its struts, reduced wing loading and so increased manoeuvrability. The fuselage was a welded steel-tube frame covered in duralumin at the front and fabric behind, and the wings had two wooden spars. The prototype flew with an imported Wright Cyclone radial surrounded by a Townend ring; production aircraft began with the M-22, a licence-built Bristol Jupiter, and switched to the licence-built M-25 Cyclone in late 1936. Armament was four PV-1 machine guns mounted to fire between the engine cylinders, with bomb racks under the wings. The gull wing was also the type's weak point: it restricted the pilot's view at take-off and landing and was blamed for poor directional stability.
Operational History
The first prototype was completed in October 1933 and made its first flight that month, with V. P. Chkalov at the controls. Production began at the start of 1934 at two Moscow state factories, Zavod 1 and Zavod 39. The first aircraft arrived at Cartagena by sea on 13 October 1936, and the I-15 made its combat debut in the Battle of Madrid in November 1936, against German Heinkel He 51s and Italian Fiat CR.32s. It proved at least the equal of the He 51, though less successful against the CR.32, and it played a major part in defeating the Italian attempt to encircle Madrid at Guadalajara in March 1937. Spain also built the type under licence: 300 were ordered and around 231 completed, operating alongside the Soviet-built aircraft from mid-1937. Soviet deliveries to Spain are themselves uncertain in the sources, totalling either 155 or 186 aircraft. Attrition was heavy: by the spring of 1938 the number of serviceable I-15s in Spain had dropped to under twenty, and the type was becoming increasingly outclassed as the Nationalists received Messerschmitt Bf 109s. From the autumn of 1937 the aircraft also fought in Asia: 255 were supplied to China that autumn with Soviet volunteer pilots, and 347 I-15s and I-15bis had been delivered by 1939; the I-15bis was used extensively at Khalkhin Gol in 1939. More than a thousand I-15bis fighters were still in Soviet use when Germany invaded in 1941, many in the ground-attack role, but most I-15s had already been replaced in front-line service by 22 June 1941, though the Black Sea Fleet's 3rd Fighter Regiment still flew the type at Sevastopol.
Afterlife
The I-15's own production total is contested: published sources disagree, one account giving 384 aircraft with all engines and others a breakdown implying roughly twice as many, so the catalog records no single figure. The I-15bis replaced the gulled wing with a longer, straight upper wing, because pilots felt the gull restricted visibility; production began in 1937 and 2,408 were delivered by 1940. The I-153 then reverted to the gulled wing and added a manually retractable undercarriage; with 3,437 built, the family total reached 6,578 aircraft. The I-15bis soldiered on in Soviet service until November 1943, by which point the survivors had all been moved to second-line work. Of the I-153, four complete survivors are reported, three of which can fly: three were restored to airworthy condition for New Zealand's Alpine Fighter Collection in the 1990s, and one is on static display at the Musée de l'Air in Paris, reported to be the only fully original I-153 known.